The invention relates to substantially inorganic mildly alkaline, anti-corrosion, metal-protecting warewashing detergent materials that can be manufactured in the form of a solid block and packaged for sale. In the manufacture of the solid detergent, a detergent mixture is extruded to form the solid. The solid water soluble or dispersible detergent is typically uniformly dispensed, without undershoot or overshoot of detergent concentration, from a spray-on type dispenser which creates an aqueous concentrate by spraying water onto the soluble solid product. The aqueous concentrate is directed to a use locus such as a warewashing machine to clean ware with no substantial corrosion of metal ware.
The use of solid block detergents in institutional and industrial cleaning operations was pioneered in technology claimed in the Fernholz et al. U.S. Reissue Pat. Nos. 32,762 and 32,818. Further, pelletized materials are shown in Gladfelter et al., U.S. Pat. Nos. 5,078,301, 5,198,198 and 5,234,615. Extruded materials are disclosed in Gladfelter et al., U.S. Pat. No. 5,316,688. The solid block format is a safe, convenient and efficient product format. In the pioneering technology, substantial attention was focused on how the highly alkaline material, based on a substantial proportion of sodium hydroxide, was cast and solidified. Initial solid block products (and predecessor powder products) used a substantial proportion of a solidifying agent, sodium hydroxide hydrate, to solidify the cast material in a freezing process using the low melting point of sodium hydroxide monohydrate (about 50xc2x0 C.-65xc2x0 C.). The active components of the detergent were mixed with the molten sodium hydroxide and cooled to solidify. The resulting solid was a matrix of hydrated solid sodium hydroxide with the detergent ingredients dissolved or suspended in the hydrated matrix. In this prior art cast solid and other prior art hydrated solids, the hydrated chemicals are reacted with water and the hydration reaction is run to substantial completion. The sodium hydroxide also provided substantial cleaning in warewashing systems and in other use loci that require rapid and complete soil removal. In these early products sodium hydroxide was an ideal candidate because of the highly alkaline nature of the caustic material provided excellent cleaning. Another sodium hydroxide and sodium carbonate cast solid process using substantially hydrated sodium materials was disclosed in Heile et al. U.S. Pat. Nos. 4,595,520 and 4,680,134.
Similarly, pioneering technology relating to the use of solid pelleted alkaline detergent compositions in the form of a water soluble bag assembly and an extruded alkaline solid material wrapped in a water soluble film has also been pioneered by Ecolab Inc. These products within the water soluble bag can be directly inserted into a spray on dispenser wherein water dissolves the bag and contacts the soluble pellet or extruded solid, dissolves the effective detergent ingredients, creates an effective washing solution which is directed to a use locus.
In recent years, attention has been directed to producing a highly effective detergent material from less caustic materials such as soda ash, also known as sodium carbonate, because of manufacturing, processing, etc. advantages. Sodium carbonate is a mild base, and is substantially less strong (has a smaller Kb) than sodium hydroxide. Further on an equivalent molar basis, the pH of the sodium carbonate solution is one unit less than an equivalent solution of sodium hydroxide (an order of magnitude reduction in strength of alkalinity). Sodium carbonate formulations were not given serious consideration in the industry for use in heavy duty cleaning operations because of this difference in alkalinity. The industry believed carbonate could not adequately clean under the demanding conditions of time, soil load and type and temperature found in the institutional and industrial cleaning market. A few sodium carbonate based formulations have been manufactured and sold in areas where cleaning efficiency is not paramount. Further solid detergents made of substantially hydrated, the carbonate content contained at least about seven moles of water of hydration per mole of sodium carbonate were not dimensionally stable. The substantially hydrated block detergent tended to swell and crack upon aging. This swelling and cracking was attributed to changing of the sodium carbonate hydration states within the block. Lastly, molten hydrate processing can cause stability problems in manufacturing the materials. Certain materials at high melting temperatures in the presence of water can decompose or revert to less active or inactive materials. The carbonate detergents could under certain circumstances corrode metal surfaces. Ware made of active metals such as aluminum are subject to such corrosion when carbonates are used as the alkalinity source.
Accordingly, a substantial need for mechanically stable solid carbonate detergent products, having equivalent cleaning performance without substantial metal corrosion, when compared to caustic based detergents, has arisen. Further, a substantial need has arisen for successful non-molten processes for manufacturing sodium carbonate based detergents that form a solid with minimal amounts of water of hydration associated with the sodium base. These products and processes must combine ingredients and successfully produce a stable solid product that can be packaged, stored, distributed and used in a variety of use locations.
The invention involves a solid block detergent based on a combination of a carbonate hydrate and a non-hydrated carbonate species with a metal protecting anti-corrosion silicate component solidified by a novel hydrated species we call the E-form hydrate composition. The solid can contain other cleaning ingredients and a controlled amount of water. The solid carbonate/silicate based detergent is solidified by the E-form hydrate which acts as a binder material or binding agent dispersed throughout the solid. The E-form binding agent comprises at a minimum an organic phosphonate and water and can also have associated carbonate. The solid block detergent uses a substantial proportion, sufficient to obtain non-corrosive cleaning properties, of a hydrated carbonate, a non-hydrated carbonate and a silicate composition formed into solid in a novel structure using a novel E-form binder material in a novel manufacturing process. The solid integrity of the detergent, comprising carbonate, silicate and other cleaning compositions, is maintained by the presence of the E-form binding component comprising an organic phosphonate, substantially all water added to the detergent system and an associated fraction of the carbonate. In the detergent blocks of the invention, the use of a sodium silicate and a sodium carbonate with a potassium phosphonate have surprisingly been found to be a preferred composition for formation of a stable rapidly solidifying block. This E-form hydrate binding component is distributed throughout the solid and binds hydrated carbonate and non-hydrated carbonate and other detergent components into a stable solid block detergent.
The alkali metal carbonate is used in a formulation that additionally includes an effective amount of a metal protecting silicate and a hardness sequestering agent that both sequesters hardness ions such as calcium, magnesium and manganese but also provides soil removal and suspension properties. The formulations can also contain a surfactant system that, in combination with the sodium carbonate and other components, effectively removes soils at typical use temperatures and concentrations. The block detergent can also contain other common additives such as surfactants, builders, thickeners, soil anti-redeposition agents, enzymes, chlorine sources, oxidizing or reducing bleaches, defoamers, rinse aids, dyes, perfumes, etc.
Such block detergent materials are preferably substantially free of a component that can compete with the alkali metal carbonate or the E-form material for water of hydration and interfere with solidification. The most common interfering material comprises a second source of alkalinity. The detergent preferably contains less than a solidification interfering amount of the second alkaline source, and can contain less than 5 wt %, preferably less than 4 wt %, of common alkalinity sources including sodium hydroxide. While some small proportion sodium hydroxide can be present in the formulation to aid in performance, the presence of a substantial amount of sodium hydroxide can interfere with solidification. Sodium hydroxide preferentially binds water in these formulations and in effect prevents water from participating in the E-form hydrate binding agent and in solidification of the carbonate. On mole for mole basis, the solid detergent material contains greater than 5 moles of sodium carbonate for each total mole of both sodium hydroxide.
We have found that a highly effective detergent material can be made with little water (i.e. less than 11.5 wt %, preferably less than 10 wt % water) based on the block. The solid detergent compositions of Fernholz et al. required depending on composition, a minimum of about 12-15 wt % of water of hydration for successful processing. The Fernholz solidification process requires water to permit the materials to fluid flow or melt flow sufficiently when processed-or heated such that they can be poured into a mold such as a plastic bottle or capsule for solidification. At lesser amounts of water, the material would be too viscous to flow substantially for effective product manufacture. However, the carbonate based materials can be made in extrusion methods with little water. We have found that as the materials are extruded, the water of hydration tends to associate with the phosphonate component and, depending on conditions, a fraction of the anhydrous sodium carbonate used in the manufacture of the materials. If added water associates not with the E-form hydrate but improperly with other materials such as sodium hydroxide or sodium silicates, insufficient solidification occurs leaving a product resembling slush, paste or mush like a wet concrete. We have found that the total amount of water present in the solid block detergents of the invention is less than about 11 to 12 wt % water based on the total chemical composition (not including the weight of the container). The preferred solid detergent comprises less than about 2.0, more preferably about 0.9 to 1.7 moles of water per each mole of carbonate. With this in mind for the purpose of this patent application, water of hydration recited in these claims relates primarily to water added to the composition that primarily hydrates and associates with the binder comprising a fraction of the sodium carbonate, the phosphonate and water of hydration. A chemical with water of hydration that is added into the process or products of this invention wherein the hydration remains associated with that chemical (does not dissociate from the chemical and associate with another) is not counted in this description of added water of hydration. Preferred hard dimensionally stable solid detergents will comprise about 5 to 20 wt %, preferably 10 to 15 wt % anhydrous carbonate. The balance of the carbonate comprises carbonate monohydrate. Further, some small amount of sodium carbonate monohydrate can be used in the manufacture of the detergent, however, such water of hydration is used in this calculation.
For the purpose of this application the term xe2x80x9csolid blockxe2x80x9d includes extruded pellet materials having a weight of 50 gram up through 250 grams, an extruded solid with a weight of about 100 grams or greater or a solid block detergent having a mass between about 1 and 10 kilograms.